Rotary expansible drill bits



Feb. 4, 1958 A. w. KAMMERERLJR 49 ROTARY EXPANSIBLE DRILL BITS Filed Aug. 25, 195 1 2 Shets-Sheet 1 2e INVENTOR. if ARCHER W K444445252, rIQ.

ATTORNE).

Feb- 4, 195 A. w. KAMMERER, JR I 2,822,149 I ROTARY EXPANSIBLE DRILL BITS Filed Aug. 25; 1954 2 Sheets-Sheet 2 a? a2 a5 84 27211. 5;

' 83 INVENTOR.

Age/1E2 WHAMMEQER, (7e.

BY as a Z Jrfaeus).

United States Patent ROTARY EXPANSIBLE DRILL BITS Archer W. Kammerer, Jr., Fullerton, Calif., assignor, by direct and mesne assignments, to Rotary Oil Tool Company, Huntington Park, Calif., a corporation of California Application August 25, 1954, Serial No. 452,183 11 Claims. (Cl. 255-76) ing members pivotally carried by the bit body, the supporting members and the cutters mounted thereon being shifted outwardly by an expander engaging the supporting members. The expander may slide relatively along tapered expander surfaces on the supporting members in eifecting outward shifting of the latter and the cutters.

Ordinarily, when the cutter supporting members are in retracted position, the expander engages them close to their fulcrums or pivotal supports on the body. Accordingly, the lever arm of the outward forceapplied against each cutter supporting member is comparatively small, the force urging the cutters against the wall of the formation also being relatively small. As the cutters shift outwardly, the expander moves relatively along the supporting members away from the fulcrums, the lever arm increasing and the outward force against the cutters also increasing. When the cutters are fully expanded, the lever arm and the outwardly directed force are at a maximum.

It is not necessary for the outward cutter expansion 7 force to increase as the cutters move outwardly. In fact,

panded position. Proper operation of the bit and long life of the mandrel and body is dependent to a great extent upon the provision of a proper splined connection between them. Heretofore, such connection has been comparatively costly to manufacture and had to be made to relatively close tolerances, to insure the appropriate coaxial position of the mandrel in the body of the expansible bit. The coaxial relation should be maintained after the cutters have been expanded fully and drilling weight is being imposed on them, for the purpose of insuring smooth operation of the bit and to minimize wear on the parts.

Accordingly, an object of the present invention is to provide an improved spline connection between the mandrel and the body of an expansible rotary drill bit, which is comparatively simple and economical to manufacture, possesses the desired tolerances or clearances between the companion parts, and insures the maintenance of a coaxial relation between the mandrel and the body.

Another object of the invention is to provide an expansible rotary drill bit embodying a mandrel slidably splined to the bit body, in which the mandrel is automatically centered and retained in a coaxial position with respect to the body during the hole enlarging operation, thereby insuring smooth functioning of the apparatus and increasing its useful life.

A further object of the invention is to insure the coaxial relation, at their slidable spline interconnection, between the mandrel and body of a rotary expansible drill bit having cutters expanded outwardly by hydraulic pressure, to minimize wear at the hydraulically actuated portion of the drill bit, and to increase the life of the sealing devices embodied in the hydraulically actuated portion.

Yet another object of the invention is to insure freedom of sliding movement between the mandrel of a rotary expansible drill bit and the main body of the bit to which it is slidably splined, by allowing comparatively free passage of fluids, sand, and the like, between the mandrel and body at their splined interconnection.

Still another object of the invention is to provide a rotary expansible drill bit having a mandrel telescopically related to the main body of the bit, in which the mandrel can forcibly retract the cutters from their outwardly expanded position, if such action becomes necessary or desirable. The mandrel can also be elfective to hold the cutters retracted during elevation of the drill bit in the well bore.

Certain rotary expansible drill bits have cutter supportit is desirable for such force not to increase. It is important to have adequate expansion force when the cutters are in their-retracted position and dig initially into the wall of the hole, particularly when operating in hard formations. To provide such initial force, the point of initial engagement between the expander and each cutter supporting member hasheretofore been disposed an adequate distance from the supporting member fulcrum. Such disposition required an increase in the length of the cutter supporting members to secure their proper outward expansion, increasing the over-all length of the drill bit and its cost. The outward force still increased as outward expansion of the cutters occurred, due to increase in the lever arm of the force applied to each cutter supporting member and an increase in the wedge angle between the expander and supporting member as the latter pivots outwardly on its fulcrum.

It is another object of the invention'to relate the expander and cutter supporting members to each other in such manner that ample initial outward expansion force can be applied against the cutter supporting members and at a point relatively close to their fulcrums, thereby enabling the length of the supporting members and the length of the body to be held to a minimum. 7 A further object of the invention is to shape the comgaging portions of the expander and cutter supporting members in such manner that the outward expansion force applied against each cutter supporting member decreases as the point of contact between the expander and cutter supporting members move further away from the fulcrum of the cutter supporting members, thereby compensating for the increased lever arm of the force applied to the cutter supporting members and preventing the application of an undesirably large force of the cutters against the wall of the hole. If desired, the outward force of the cutters against the wall of the hole can be kept substantially constant as expansion of the cutters proceeds to the maximum extent. Again, instead of the force against each cutter supporting member decreasing as the point of contact between the expander and'the cutter supporting member moves away from the fulcrum of the cutter supporting member, the forces applied may be held constant or be prevented from increasing to any substantial extent.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. .This form is shown in the drawings accompanying and forming part of the present specification.

It will now be described in detail, for the purpose er illustrating the general principles of the invention; but it;

. Patented Feb..4, lass.

3 is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section through an embodiment of the invention disposed in a Well bore, with the cutters and otherparts in their initial retracted positions;

Fig. 2 is a longitudinal section similar to Fig. 1, disclosing the cutters locked in their fully expanded position;

Fig. 3' is an enlarged fragmentary section disclosing the cutter and expander portions of the device, with the cutter in retracted position;

Fig. 4 is a view similar to Fig. '3, with the cutter locked in its fully'expanded position;

Fig.5 is a cross-section, on an enlarged scale, taken" along the line 5-5 on Fig; 1.

As shown in the drawings, a rotary expansible drill bit A is'secured'to'the lower'errd "of a string of drillpipe B extending to the top of the well boreC, and by means of which the drill bit is lowered through a string of well casing D to a region therebelow' where the hole enlarging operation is to'comm'ence. The general type of expansible drill bit disclosed in the drawings is shown and described in Patent No. 2,545,036, to which attention is invited for certain structural details.

The upper'portion of the rotary drill bit consists of a mandrel 16 having an upp'erpin 11 thre'adedly connected to a sub 12 forming the lower end of the string of drill pipe B. This mandrel includes an upper kelly or drill' stem 13 slidably 'splined to the main'body 14 of the drill bit. The exterior 15 of the lower portion of the kelly is non-circular in shape, being telescopically received in a companion'non-circular socket 16 provided in the main bit body, the kelly 13 being capable of moving longitudinally with respect to the body 14 and also being capable of transmitting rotary movement thereto.

The mandrel It! has a limited range of'longitudinal movement'within thejbody 1'4, its downward movement being determined by'engagement of the lower end 17 of the kelly with an inwardly directed body shoulder 18, and its upward movement being limited by engagement of an external shoulder or piston portion 19 of the kelly with one or more stop rings 20 that may be split to enable them to be inserted'within an internal groove 21 in the main body of the'bit; the stop rings extending into a cylinder space 22 formed between the kelly or drill stem 13 and the body 14' of the tool. It is to be noted that the coengageable surface of thelower end 17 of the kelly and the inwardly directed body shoulder 18 are frustoconical' in shape, tapering in a downward and inward direction, in order that the engagement of the lower end of the kelly with the shoulder will tend to center, and insure the retention of the kelly 13 in a central and coaxial position, within the body1'4 of the tool;

The body 14 has a plurality of expansible parts mounted on it. These includecutter supporting members 23 pivotally mounted in body slots '24 on hinge pins '25 suitably secured to the body to prevent their loss therefrom. Each cutter supporting member 23 has a leg portion 23:: depending from the hinge pin 25 and terminating in a bearing supporting pin 26 inclined inwardly and downwardly. A side roller cutter 27 is rotatably mounted on each bearing supporting pin26, being mounted upon'antifriction roller and ball bearing elements 28,. 29 rol1ab1 e on the bearing supporting pins. The ball bearing elements 29 serve to lock the cutter 27 against endwise movement on the bearing supporting pin 26, as wellas to transmit axial and radial thrusts, the roller bearingelements 28 transmitting primarily radial thrusts. The manner of mounting the ball and roller bearingelements 29, 28 between the cutter 27 and bearing supportingmember 26 is specifically described in the. above-mentioned Patent No. 2,545,036, towhich attention is invited.

Each cutter supporting member 23- and cutterv 27"tend to occupy a retracted position substantially entirely within the confines of the main body 14 of the bit. These cutter supporting members and their cutters are expanded outwardly to enlarge the sides of the well bore C and to operate upon a formation shoulder E that the cutters form in the latter. To accomplish the expansion, each cutter supporting member 23- has an inclined expander surface 30- on its inner portion 31 below the hinge pin 25 which tapers in a downward and inward direction. Each expander surface 30 merges smoothly into and terminates in alock surface Lil-formed on a lock portion 33 of the cutter supporting member. The outward expansion is accomplished by producing relative longitudinal movement between the mandrel 1t) and the bit body '14, which will produce the relative longitudinal movement between the cutter'supporting members 23 and a tubular member 34 of the mandrel. This tubular member 34 includes a lower portion 35 slidable within a guide 36 secured to the'body '14 and extending across the body slots'24; This guide is disposed below the lock portions 33' of the cutter supporting members23.

Located initially substantially above the guide 36 and below the hinge pin 25 and in cutter member recesses 37 is a mandrel lock and expander 38 which has outer surfaces 39'ad'apte'dtoen'gage' the expander surfaces 30' and thelock surfaces"32. The lock and expander 38 may be formed integral with the tubular member 34, the upper end ofthe' latter being piloted within a socket 40 formed'in the lower portion of the kelly 13. An enlarged boss 41 on the tubular member engages a downwardly facing shoulder 42 'of'the kelly, the tubular member beinghe'ld" against this shoulder by a suitable split retainer or lock ring 43' snapped into an internal groove 44 encompassing the" kelly socket 40 and engaging a downwardly directed shoulder 45 formed on the tubular member boss 41.

To facilitate passageof'drilling or other fluid down through the central passage '46 of the kelly or drill stem 13 and into the central passage 47' extending completely through the tubular member 34, the latter has'a portion 48exterrdin'g upwardlyfrom' its boss 41 and provided with an upwardly flaring end '49 merging smoothly into the lower tapered surface 50 of the kelly passage 46. Leakage of fluid around the exterior'of the tubular member 341s prevented'by'a suitable side seal ring' 51, such as a rubber O ring, 'located'in a' peripheral groove 52 in the boss 41, which engages the wall of the kelly socket 40.

Assuming'that' the body 14 of the tool is elevated relatively along the tnbular mandrel 10; the inclined expander surfaces 30 of thecutter supporting members 23 will be shifted upwardly'along the lock and expander portions '38 of: the tubular member; During'su'ch upward shifting, the cutter supporting-members'2'3' and'the cutters 27 carried thereby will be pivoted about the hinge pins '25 and urged in'arr'outward direction. The upward movement of the body 14"with respect to the tubular mandrel 10' can continue until the-cutters 27 have shifted outwardly to their fullest extent, as'determine'd by engagement of stop shoulders 53--on' the cutter supportingmembers with companion shoulders'54 formed in the body on opposite sides, of the body' slots 24. When'such engagement occurs,-'the lower end 1 7 'of the kelly portion of thetubular mandrel 10 will engage the body shoulder 18', and the lock and expander 38 onthe tubular member 34will'be disposed'behindandin engagement with the lock portion 33 on the cut-ter supporting *rnembers '23. 7

It is to be noted 'that"the surfaces' 32 ofthe lock por tions of the cutter supporting members 23 and the companion surfaces 39 -on the-1och andexpander portions 38 oflthe: tubular-member are substantially parallel to theaxis' .ofi-the'dr ilhbit when the cutters-are fully expanded, tonprevent"thereactive forces of the formation on the cutters 2'T;ifrom moving the latter inwardly. As

a practicalematte'r, itispreferred that-the coengagin'g lock surfaces 32, 39 be inclined slightly in a downwardndirectiontoward the axisof the tool gto insure release-ofthe lock and expander portion 38 from the-cutter supporting members 23 when the latter and the cutters 27 are to be shifted to a retracted position.

In the specific form of the invention disclosed in the drawings, the relative longitudinal movement between the tubular mandrel and body 14 of the tool is accomplished hydraulically. Thus, the piston or enlarged portion 19 on the drill stem 13 is received within a counterbore 60 formed on the upper portion 14a of the body 14 of the tool. stitutes a cylinder having a cylindrical wall 61 extending from a lower shoulder 62, defining the bottom of the counterbore, to an upper head and guide 63, which has a depending portion 64 inserted in the upper end of the cylinder and releasably retained therein by a split snap ring 65 carried in a groove in the cylinder portion 64 and adapted to be received within a generally V-shaped internal groove 66 in the upper portion of the cylinder wall 61. The head 63, with the snap ring 65 therein, need merely be forced into the cylinder 14a, and when located opposite the V-shaped' groove 66, the snap ring will expand inherently partially into the latter to releasably lock the cylinder head 63 to the cylinder 14a.

The confined cylinder space 22 is formed between the piston portion 19 of the kelly 13, the periphery of the kelly above the piston, and the cylinder 14a. A suitable packing or side seal structure 67 may be disposed in a suitable piston ring groove 68 formed on the piston 19, which is adapted to slidably seal against the cylin drical wall 61 of the cylinder 14a. Fluid is thereby prevented from passing in a downward direction between the piston 19 and the cylinder 14a. Similarly, fluid is prevented from passing in an upward direction out of the annular cylinder space 22 by a cylinder packing or sealing structure 69 secured to the cylinder 14a and slidably engaging the periphery ofthe kelly 13. This structure may take any suitable form. As disclosed, it consists of a lower packing supporting ring 70 resting upon the split retainer ring 20 received within the internal groove 21 in the cylinder 14a. A non metallic packing 73, which may be made of any suitable material, rests upon the ring 70, with its upper end engaging an upper backing ring 74 bearing against a split retainer ring 75 received within an internal groove 76 in the cylinder 14a. The outer upper portion 75a of the retainer ring 75 and the adjacent upper wall of the internal groove 76 are preferably inclined in an upward and inward direction, in order that the split retainer ring 75 will be forced inwardly out of the groove 76 when it is subjected to a sufficient upwardly directed longitudinal force. It is evident that the upper and lower split retainer rings 75, 20 prevent longitudinal movement of the packing structure 59 with respect to the bit body cylinder 14a, th'e non-metallic packing portion 73 of the sealing structure 69 engaging the cylinder Wall 61 to prevent leakage therealong, and also slidably engaging the periphery of the drill stem portion 13 of the tubular mandrel 10.

Fluid under pressure in the string of drill pipe B and in the tubular mandrel 10 can be fed into the cylinder space 22 through one or more side ports 77 establishing communication between the central passage 46 through the kelly 13 and the cylinder space. Such fluid under pressure is developed in the form of invention disclosed in the drawings by virtue of the fact that the passage 47 through the tubular member 34 of the mandrel is of a restricted diameter as compared to the passage 46 through the kelly portion 13 of the mandrel. As a result, the pumping of drilling mud, or other fluid, at an adequate rate through the passage will buildup a back pressure of fluid in the passage 46, which pressure will be imposed on the fluid in the cylinder space 22 acting upon the packing structure 69, to urge the body 14 of the tool in an upward direction with respect to the tubular mandrel 10, to secure the outward expansion of This upper portion 14a actually con the cutter supporting members 23 and cutters 27 to their fullest extent. a

For the purpose of securing the proper cooperation between the tubular mandrel 10 and the body 14 of the tool, the slidable spline connection 15, 16 therebethem during the performance of the hole enlarging operation. As described above, the lower portion 15 of the kelly 13 is non-circular in cross-section, and this is also true of the companion socket 16 formed in the body 14 of the tool above its lower tapered shoulder 18. Actually, the non-circular configurations described above lie partially on sections of circles, to enable the desired coaxial relationship to be obtained between the parts (Fig. 5). Thus, the exterior 15 of the lower part of the kelly is first formed with a cylindrical shape 80, the cylinder having the required external diameter. Similarly, the socket 16 in the body, which lies between the counterbore shoulder 62 and the lower stop shoulder 18 on the body, is also bored out to provide a cylindrical wall 81 having the requisite diameter, which is only greater than the external diameter of the kelly surface suificient to provide the necessary working clearance between these parts. Opposite portions of the lower kelly region are then flattened, as by milling away the material, to provide the opposed flat sides 82. Companion flat surfaces 83 are provided in the body socket. Specifically, such flat surfaces are formed on opposed wear members or shoes 84 of segmental shape having arcuate outer sur-' faces 85 of a curvature conforming to the inner Wall 81 of the socket 16. tegrated to the body 14 of the tool by providing lateral holes 86 through the wall of the body through which welding material 87 can be deposited, to firmly secure the wear members to the body of the tool. The wear members 84, of course, extend from the lower end of the counterbore 60 substantially to the lower shoulder 18 of the body 14.

By virtue of the splined connection described, the mandrel 10 can shift longitudinally with respect to the body 14, and will be held in a coaxial position relative thereto by virtue of the coengagement between the opposed arcuate surfaces 80 on the exterior of the mandrel with the circular wall 81 of the body. When the mandrel is rotated, the turning effort is transmitted to the body of the tool through the coengaging flat surfaces 82, 83 on the mandrel andthe wear members or shoes 84.

Accordingly, as the mandrel 10 moves downwardly relative to the body 14 in accomplishing the outward expansion of the cutter supporting members 23 and of the cutters 27, proper coengagement between the expander 38 on the tubular member 34 with the expander surfaces 30 on the cutter supporting members is assured, since the mandrel is held in the coaxial position with respect to the body. Moreover, following full expansion of the cutters, the tapered lower end 17 of the kelly 13 engages the companion tapered shoulder 18 on the body, which will tend to center and retain the mandrel 10 centered with respect to the body of the tool.

A comparatively simple splined arrangement has been provided that insures against the tilting of the mandrel 10 within the body 14, or any material play therebetween.

Substantially all of the lateral forces between the mandrel and the body are transmitted through the splined connection, the sealing portions 67, 69 on the piston 19 and the cylinder 14a being relieved of such lateral forces or play, which insures the proper sliding of the seals against their companion surfaces, holding the wear on the sealing parts of the hydraulic portion of the apparatus to a'mini- I mum.

A t ebo y 1,4 o the tool is shifted relatively in an These wear members 84 are in- I upward directionito 'expand"the cutter supponingimem:

bers.23 and the cutters 27 outwardly, the expander. 38'" 23" swingoutwardly, the tapered l expander surfaces 30" will beihclined at 'a"prog'res's'iv'ely greater angle to' the horizontal or at a' lessenang'le'to' the vertical. tapered'isurf'aces 30 Were'straight, then the laterally out ward directed'compon'e'nt of thelongitudinal force of the expanderflos'uponthesesurfaces-would increase as the points of contact of the iexp'anderagainst each expander surface moved furtherawa'y from the hinge pinfu'lcrum? 25'. Accordingly," the" outwardforceof'such cutter 27 against the wall"of th'eforination, in producing the formationshoulder E; would be increased substantially over the initialoutwardforce when the cutters occupy substantially their "fully retracted position. The increase in force would be"due"to-an'-increase'ofthe tangent angle to the horizontal (or 'a'plane normal 'tothe' axis of the tool) at the point'of 'contact'of theexpan'der 38with the expander surface"39;'as such point offcontact' moves'further away from the fulcrum pin"25,'and it 'is 'also'due'to the increase of the lever arm of the'forc'e at the point of engagement-as the latterm oves further away from the hinge pin; Accordingly, the initial expansion force applied would he at a minimum'when thecutters 27 are 'in substantially their fully retracted positions, and steadily increases to amaximu'm as thecutters are expanded'outwardly; In the present instance'dt'is proposed to increase the amount of force-that the'cuttersexert against the wall of the formation when the "cutters are insubstantially their fully'retracted position, and not to increase such force substantially, or, for thatmatter, to actually hold such force constant-and even'decreaseitas the cutters move laterally outward of their maximum expanded position.

The expander surface 30 "on th'e'inner portionof each cutter supporting member 23 maybe formed as a concave curve. This'curve is shaped in such manner that, when a cutter supporting member 23 is in its fully retracted-position, the expander 38wi'll engage the expander surface iall 'on the cutter-supporting member at a point 90- at which a tangent 91 (Fig. 3) drawn to this point of contact will be relatively steeply pitched, or make a compartively large angle with the horizontal (assuming the tool to be disposed with its axis in a vertical position), The-lateral outward or horizontal force on the cutter supporting member 23 under these conditions is dependent upon the tangent of the angle that the tangentline 91 makes to the horizontal. T bus, the value of the natural tangent of this angle will provide amechanical advantage that-the outwardly directed force will have with respect to the longitudinal force exerted between the expander 38 and the expander surface 30, and, in view of the provision of a relatively large tangent-angle, the mechanical advantage will be relatively great. Accordingly, with a steeply pitched tangent 91 to the point of contact 94), when each cutter supporting member 23 is in itssubstantially fully retracted position, a-large outwardlydirected force can be imposed on the cutter supporting member, despite the fact that the point of contact 9ilis then comparatively close to the fulcrum or hinge pin 251 As the expander 33 moves relativelyinadbwnward direction along the expander surface 39, the point of'contact 92 against the latter moves away from the hinge pin 25, increasing the lever arm andthe force that the cutter 27 could apply against-the wall of the formation. How-' ever, in the present instance, suchincr'ease' in lever arm is compensated by the fact that the expander surface is curvedin su'ch' a manner that asthe point of contact moves away from the hinge pin, a line-93drawn to such point of contact makes a lesser angleto the horizontal, and -suchlangle w'ill progressively decrease as the point tlie .extenn to further expand the-cutters outwardly.

of contacfmoves 'furthefaway from the hingepin 25; Inasmuch"as th'en'atur'a'l' tangent'of such angle willidecrease, .so will the mechanicaladvantage .of the force appliedbyth'e 'expander38 against the cutter supporting member2j3.'f Accordingly, despite anincreas'e in the leverarm as the point of contact moves further'awa'y from the"fulcru-m"25, the mechanical advantage is decreased, resulting in the'maintenance ofthe force of' each cutter 27 against' the wallof the formation substantially constant, 'onat'least, such force will not increase to as great an extent as before. the shape'of the. expander'curve 30; the force can actually be "decreased."

The-decrease in the angle of the tangent that the point of contact makeswith'the horizontal, or'plane normal to the axis'of'the tool, occursdespite' the fact'thatthc cutter'supportingmember '23 is swinging in anoutward direction andtends to'cause the tangent to the point of contactto assume a more steeply pitched angle. This is clear from Fig. 3, in which the line 91 tangent to the point ofcontact 98,'when the-cutter supporting member is in'its retracted position; will makea greater angle to a plane'normal to the axis'of the tool-than the line 93 drawn to thepoint of contact 92, designated in broken lines'in the drawings; following'partial expansion of the cutter'supporting memberandthe cutter in-an outward direction? AsafOrestated, the lower'portion 'of the curved expandersurface 30 preferably "merges smoothly into the holding'or lock surface 32 provided on the lock portion 33'of each cutter supportingmember 23, insuring a smoothtransfe'r' of the expander and retainer member 38*from theexpander surfaceSt) of each cutter supporting mem'berinto full engagement'with the lock surface 32"0f each cutter supporting member.

Wh'en-the rdtary-enpansible -drill bit'A-is run in the merely sliding along the casingwall'during descent of the apparatus. When the'apparatus'has been lowered below thecasingshoe F, the pumps at the top of the well bore 'are started, to pump fluid at a sufiicient rate through the drill pipe B and'the tubular rnandrel passages 46, 47. Pumping of the fluid builds up a back pressure in the kelly passage 46 and inthe fluid in the ports 77 and cylinder space 22, which pressure will act upon the cylinder packing structure 69, to urge the body 14, the cutter supporting members 23 and cutters 27 in an upward direction'with'respect to the mandrel 10.

During-such upwardmovement, the upper ends of the expander surfaces SQ-onthe cutter supporting members 23 are brought to bear against the lock and expander portion- 38 of the mandrel, the cutters 27 being urged in an "outward direction againstthewall of the well bore C.- As stated above,: a line 91 drawn to the point of contact 99 and tangent thereto will make a relatively steeply pitched? angle with rcspect to a planenorinal to the axis of the tool; insuring 'a maximum mechanical advantagesof-the for-cebeing applied between the lock and expander. portion 'SS of Ithe'mandreland each cutter supporting member. The drill pipe'B and the rotary drill A are rotated atthe proper speed, while fluid is being pumpedithrough the apparatus, the cutters 27 enlarging the wellbore-without the drill pipe being movedvertically; As-"the cutters enlargethe well here, the hydraulic force. actingmponthe" body it raises the latter, the cutter supporting members-23, and the cutters 27 to a further During. such elevatioual movement, the point of contact 92 betweeni the expandecporti'on 38 of the mandrel and theexpander' surfaces 38 moves further away from the" fulcrum pins 25, to increase the lever arm of the force being imposed by' the-expanderportion P 38 onthe' cutter As 'arnatter of fact, depending upon Supporting members. However, due to the shape of each expander surface 30, a line 93 drawn to the point of contact between the expander portion 38 and this surface, and tangent to such point of contact, will make a lesser angle to a plane normal to the axis of the tool, thereby decreasing the mechanical advantage of the force being applied between the expander portion 38 of the mandrel and the cutter supporting member 23. The net result is the imposition of the proper force of each cutter 27 against the wall of the well bore.

As the cutters continue to enlarge the well bore, the body 14'is raised relatively along the mandrel toa greater extent, to elevate the cutter supporting members 23 along the lock and expander portion 38 of themandrel. The lever arm of the force transmitted from the expander portion 38 to the cutter supporting members 23 continues to increase. However, the mechanical ad vantage of the force transmitted between the two members continues to decrease, in view of the fact that the tangent to the point of contact between the parts con-. tinues to make a steadily lesser angle with the plane normal to the axis of the tool. supporting members and cutters will be shifted outwardly to their maximum extent as determined by engagement of the supporting member .stopshoulders 53 with the companion body stop shoulders 54, and the engagement of the body shoulder 18 with the lower end 17 of the kelly portion 13 of the tubular mandrel 10. As explained above, with the parts in this position, the lock portion 33 of the cutter supporting members 23 will bear against the lock and expander portion 38 of the tubular member 34, to preclude inadvertent partial retraction of the cutters 27 to their fully expanded position.

Downweight of the proper amount can now be imposed on the string of drill pipe B, this downweight being Eventually, the cutter transmitted through the kelly 13 to the body shoulder 18 and from the body through the stop shoulder 54 directly to the cutter supporting members 23 and the cutters 27, urging the teeth of the latter into the transverse formation shoulder E previously produced, in order to drill away the formation shoulder and enlarge the well bore' In the event it is desired to retrieve the apparatus A from the well bore after the hole enlarging operation has been completed, or as a result of the cutters 27 becoming worn, it is only necessary to discontinue the pumping of the drilling fluid through the drill pipe B in the apparatus, to relieve the pressure in the cylinder 13a, and to elevate the drill pipe. Such elevating movement will elevate the tubular mandrel 10 with respect to the body 14 and the cutter supporting member 23, to raise the lock and expander portion 38 above the expander surfaces 30, whereupon the cutters 27 can drop back to their retracted position. In the event the cutters are reluctant to move to their retracted position, the outer surfaces of the cutter supporting members 23 will engage the casing shoe F, which will then force them inwardly,

whereupon the apparatus can be withdrawn through the well casing D to the top of the hole.

cutter supporting members and cutters in such retracted position, the tubular member 34 of the mandrel is provided with an enlarged portion 95 above its expander 38 having an upwardly facing shoulder 96 adapted to engage downwardly facing surfaces 97 on relatively short arms 23b on the'cutter supporting members 23 extending laterally inward from the fulcrum pins 25. Following the relieving of the hydraulic pressure within the apparatus, and the elevation ofthe mandrel 10 with respect to the body 14,'the expander and retainer 38 is' i moved upwardly along the cutter supporting'members23, to allow the latter to drop back to their retracted position under theaction of gravity. In the event the cutter shoulder .96 on the mandrel will be engaging the cutter supporting member arms 23b steadily; exerting a continuing upward force therein; tending to hold the leg portions 23a of the cutter supporting'members 23.and the cutters 27 in their full inward positions.

In the event IthCQCYIlDdCPSPaCG 22 becomes packed with sand, which will not allow the mandrel 10 to move;

upwardly within the'body 14 freely, the apparatus will be elevated until the cutter supporting members 23 engage the casing shoe F, whereupon the taking of a sufficient upward strain on the mandrel will cause the sand to engage "the packing structure 69 and force the split snap ring -inwardly out of its groove 76, carrying it upwardly into engagement with the cylinder head 63, whose retainer ring'65 will also be urged out of its groove 66, allowing the mandrel 10 to shift upwardly within the body 14" and enabling the cutter supporting members23 to retract to their fullest position. Such retraction will beasSiste'd, if needbe, by the engagement of the tubular mandrel shoulder 96 with the cutter supporting member arms 23b. In this connection, if the snap rings 20 were not present in the cylinder for engagement by the piston 19,- the'release of the packing structure 69 and of' the cylinder head 63in'the manner described would allow the mandrel 10to continue moving upwardly within the V body of the tool. However, such u pward movement is definitely limited by engagement of the mandrel SlIlOUl? der 96 with the cutter supporting arms 23b and by the v fact that the cutter supporting members. can move in-f f wardly only to'the extent determined by their engagement with the tubular member. portion.34 of the mandrel or the lower guide 36. I I

Accordingly, the apparatus! will then be removed as a unit and withdrawn to the top of the hole.

Any drilling fluid and other; matetjall that might be disposed in the counterbore 60 below. the piston 19 of the mandrel may have a tendency to remain packed therein. For'eign s'ubstances, such as sand in the drilling mud, may also tendto pack i the apparatus. 1 Accordingly, the outer circular portions of the kelly below the piston 19 are preferably pro extending fromthe piston down to the lower end 17 of the kelly.- Such flutes or grooves 98 faci1itate the passage and bind in this region of vided'with 'ci rcumferentially spaced flutes or grooves 98' belowthe counterbore 60, and.

preclude binding of such foreign materials therebetween. I

Despite the presence of the flutes or grooves 98, the

periphery 80' of the kelly will still make a comparatively. I

close fit'withthe circular wall portions 81 of the body 14 of i the total; to maintain the mandrel, 10 coneentrically disposed with respectto" the body of the tool,

The inventor claims a v v s 1. .In a rotary well drilling bit; a main body; cutter means pivotally. ,mounted on said body for expansion.

laterally outward of saidbody; meansforexpanding and r holding said cutter means laterally. outward, said expanding and holding meanscomprising a. mandrel connectible Y i to a drill string and telescoped within said bodyfor longi-- tudiual. movement with respect thereto .and engageable withsaid cuttermeans on one-side of its'pivot axis to h ld said cutt r m nsIla s all ..-e twatlta ?seawater able means on said mandrel and cutter means to exert a V forceon said cutter means in.a direction onrtheoppositej side of its pivot ,axis forxretracting said.cutter.means from its expanded position, upon upward movement of said mandrel within said body.

2. In a rotary well drilling bit: a main,body;;a cutter supporting member pivotally mountedyon said body for expansion laterally outward of saidxbo yt. av cutter ,on

said supporting member; means for expanding andhold -wing said supporting member and cutter laterally outward, said expanding and holding means comprising a mandrel connectible to a drill string and telescoped fwithinsaid body for longitudinal movement with .respect thereto; said mandrel engaging said supporting member on one side of its pivot axis to. hold said cutter laterally outward; and means on said mandrel engageable with means on. said supporting member to exert a force on said supporting member in a direction on the opposite side of its pivot.

axis for shifting said supporting. member and cutter to;

retracted position upon upward movement of said man-v drel within said body.

3. In a rotary well drilling bit: a main body; a cutter supporting member pivotally mounted on said body for expansion laterally outward of said body; a cutter on said supporting member; means for expanding and holding said supporting member and cutter laterally outward, said expanding and holding. means comprising a mandrel connectible to a drill string and slidably'splined within said body, said mandrel being movable; downwardly. within said body to a position engageable with said sup-1 porting member on one side of its pivot axis to-hold said supporting member and cutter in their outwardly expanded position; and means on said mandrel, engage: able with means on said supporting member to exert a force on said supporting member in a direction on the opposite side of its pivot-axis to shift said supporting member .and cutter to retracted position upon upward movement of said mandrel within said body.

4. In a rotary welldrilling bit: a main body; a cutter supporting member pivotally mounted on said body for expansion laterally outward of said body; a cutter on said supporting member; an operating member movable longitudinally relative to' said body and engageable with said cutter supportingmember to expand said cutter supporting member and cutter laterally outward;rone of said members engaging an. expander surface on the;-,other,

of said membersltof effect such expansipu; aid expande surface; being of such shape that adangenttp hesp intt.

of contact between said surface and said-oneof ,said; members makes ardecreasing angle to a-PIQHQILOUIIQ to, the axis of the vbody as said cutter-supportiu ..member-- and cutter are :shiftedilaterally outward.

5. Inratrotary wellv drillingbit: a main-body; ajzcutter supporting member pivotally vmounted on said; body for expansion laterally -outwardtof said. body; a cutter onc. d s pp ing emb n ope a ina embe ov l longitudinally relativeltolsaid bodyand engageable with said cutter supporting member toexpand said cutter sup; porting member tandcutterl laterally outward; one of said. members engaging antexpander surface on the other-of: said members to effect such expansion; said expandersnrface being of lsuchtshape that a tangent to'the point of contact between said surface and said one ofsaid mern-. V

' said one of said members makes when said cutter supi-.

portingmember and cutterare insubstantially their fully retracted'position with respect to said body,

6f In'arotary well drilling bit: a mai n body; a cutter; V

supporting -mernber pivotally mounted on said body for expansion laterallyp outward of said 'body; *a'cutter'on, saidsupporting-member anoperating member-movable longitudinally relative to saidbody and engageableiwith' said cutter supportingrnember to expand said cutter sup-" porting member and cutter laterally outward; said cutter, supporting member having an expander surface thereon engaged by said operating member to effect such expansion; said expander surface being of such shape that a tangent to the point of contact between said surface and saidtfoperating member makes a decreasing angle to a plane normal to the axis of the body as said cutter supporting member and cutter are shifted laterally outward. 7.'In a rotary well'drilling bit: a main body; a cutter supporting member pivotally mounted on said body for expansionlaterally outward of said body; a cutter on saidsupporting member; an operating member movable longitudinallyl relative to said body and engageable Withsaid cutter supporting member to expand said cutter support: ing member and cutter laterally outward; said cutter sup-v operatingmember, as said cutter supporting member and.

cutter move laterally outward, makes an angle to a plane ,normal to the axis of the body no greater than the angle that the tangent to the point of contact between said surface and said operating member makes when said cutter supporting member and cutter are in substantially their fully retracted position with respect to said body.

8, In a rotary well drilling bit: a main body; a cutter supportingtrnember pivotally mounted on said body for expansion laterally outward of said body; a cutter on said supporting member; an operating member movable longitudinally relative to said body and engageable with said-cutter supporting member at a progressively greater distance from the pivot of said cutter supporting memberto expand said cutter supporting member'and cutter laterally outward; one of said members engaging an expander surface on the other of said members to effect suchexpansion; said expander surface being of such shape that a'tangent to the point of contact between said surface and said one of said members makes a decreasing angle to aplane normal to the axis of the body as said point ofcontact moves further away from the pivot of said cutter supporting member.

9 In airotary well drilling bit: a main body; a cutter supporting member pivotally mounted on said body for expansion llaterally outward of said body; a cutter on said; supporting, member; an operating member movable longitudinally relative to said body and engageable with said-cutter supporting member at a progressively greaterdistance from thepivot of said cutter supporting member to expand said cutter supporting member and cutter laterally outward; one of saidmembers engaging an ex-V- pandersurfacexon thesother of said members ;to effect such expansiQm-saidexpander surfacebeing of such shape, that atangent totthe. point vofcontactbetween said suri face andtsaid one of said members, as said contact point moves away from, the pivot of. said cutter supporting member, 'makes an angletto. a plane normal to the axis;

of=thez bodylnoagreater than the angle. that the tangent to th'epoint of contact between saidsurface and said one of saidzinemb'ersrnakes when said cuttervsupporting member and cutter are in substantiallyltheir fully retracted position withtrespect. to said body 10.- Inaa rotary well drilling bit: asmain body; a cutterzsupporting member pivotallylmounted .on said body forexpansiorilaterally'loutward of said. body, said cutter supportingrmember:depending from its pivot; a cutter on afhe 7 lower portionuof said cutter l supporting member; a an operatingmember movable downward relative .to said body-and%engageable with said cutter supporting member -at a progressively: greater distance from the pivot V of saidcuttersupportingmernber to'expand saidc'utt er 'fdsup'rrorting-mer'nbr andcuttenlateraliY outward; saidcutter supporting member having an expander surface thereon engaged by said operating member to eifect such expansion, said surface being inclined inwardly and downwardly when said cutter supporting member and cutter are in their retracted position with respect to said body; said expander surface being so shaped that a tangent to the point of contact between said operating member and surface makes a decreasing angle to a plane normal to the axis of the body as said operating member moves downward relative to said body and said point of contaet moves downward further away from the pivot of said cutter supporting member.

11. In a rotary well drilling bit: a main body; a cutter supporting member pivotally mounted on said body for expansion laterally outward of said body, said cutter supporting member depending from its pivot; a cutter on the lower portion of said cutter supporting member; an operating member movable downward relative to said body and engageable with said cutter supporting member at a progressively greater distance from the pivot of said cutter supporting member to expand said cutter supporting member and cutter laterally outward; said cutter supporting member having an expander surface thereon engaged by said operating member to efiect such expansion, said surface being inclined inwardly and downwardly when said cutter supporting member and cutter are in their retracted position with respect to said body; said expander surface being so shaped that a tangent to the point of contact between said operating member and surface, as said operating member moves downward relative to said body and said point of contact moves downward further from the pivot of said cutter supporting member, makes an angle with a plane normal to the axis of the body no greater than the angle that the tangent to the point of contact between said operating member and surface makes when said cutter supporting member and cutter are in substantially their fully retracted position with respect to said body.

References Cited in the file of this patent UNITED STATES PATENTS 274,740 Douglass Mar. 27, 1883 1,839,767 Lopez Jan. 5, 1932 1,921,135 Santiago Aug. 8, 1933 2,545,036 Kammerer Mar. 13, 1951 2,699,921 Garrison Jan. 18, 1955 2,755,070 Kammerer July 17, 1956 2,758,819 Kammerer Aug. 14, 1956 

